Method for processing data associated with location area update in a wireless communication system

ABSTRACT

A method of updating control information related to a location of a user equipment (UE) supporting a first type network and a second type network different from the first type network. The method according to one embodiment is performed by the UE and includes, when the UE enters a cell of the second type network from the first type network, determining to start a location updating procedure which updates a location area of the UE if a mobility management (MM) back-off timer in the UE is running, the UE&#39;s Temporary Identity used in Next update (TIN) is set to a Global Unique Temporary Identity (GUTI), and a location area of a current cell is equal to a location area stored in the UE; and starting the location update procedure. The MM back-off timer is a timer running when an MM back-off timer value is received by the UE.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application for patent is a Continuation of Copending U.S.application Ser. No. 13/631,528, filed on Sep. 28, 2012, which claimspriority under 35 U.S.C. §119 to U.S. Provisional Application Nos.61/541,959 filed on Sep. 30, 2011, 61/556,129 filed on Nov. 4, 2011, and61/589,817 filed on Jan. 23, 2012, and International Application No.PCT/KR2012/007738 filed on Sep. 26, 2012, all of which are herebyexpressly incorporated by reference into the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The technical features of this document relate to wirelesscommunications, and more particularly, to a method for processing dataand performing a location area update procedure in a wireless networkcomprising different radio access networks.

2. Related Art

The Third Generation Partnership Project (3GPP) Long Term Evolution(LTE) which is a set of enhancements to the Universal MobileTelecommunications System (UMTS) is introduced as 3GPP Release 8. The3GPP LTE uses orthogonal frequency division multiple access (OFDMA) fora downlink, and uses single carrier frequency division multiple access(SC-FDMA) for an uplink, and adopts multiple input multiple output(MIMO) with up to four antennas. In recent years, there is an ongoingdiscussion on 3GPP LTE-Advanced (LTE-A), which is a major enhancement tothe 3GPP LTE.

3GPP LTE technology supports packet based services associated with apacket switched domain (PS-domain) only, however 3GPP does specifyfallback for circuit switched services associated with a circuitswitched domain (CS-domain) as well. In LTE architecture, theCS-fallback in an Evolved Packet System (EPS) enables the provisioningof voice and traditional CS-domain services. To provide these services,LTE may reuse CS infrastructure when the UE is served by LTE.

SUMMARY OF THE INVENTION

The technical features of this document provide a method and wirelessapparatus for performing UE's location area update in a communicationsystem comprising two different radio access network (e.g., E-UTRAN andGERAN/UTRAN). In the communication system, various entities such as MME,VLR, RNC and VLR are included.

In one aspect, the method includes: performing a combined track areaupdate (TAU) to the first type network; receiving a PS mobilitymanagement (MM) back-off time value from the first type network;starting a PS MM back-off timer based on the received PS MM back-offtime value; and when the UE moves from a first cell of the first typenetwork to a second cell of the second type network, starting a locationarea update procedure, which is associated with the CS domain, while thePS MM back-off timer is running, wherein the first cell and the secondcell belong to a same location area, which is associated with the CSdomain.

The method further comprises receiving a TAU accept message indicatingwhether an idle mode signalling reduction (ISR) function is enabled.

The method further comprises performing an intersystem change from thefirst type network to the second type network before starting thelocation area update procedure.

In the method, the UE's a Temporary Identity used in Next update (TIN)is set to a Global Unique Temporary Identity (GUTI)

In another aspect, a user equipment (UE) is further provided. The UEcomprises a processor configured for: performing a combined track areaupdate (TAU) to the first type network; receiving a PS mobilitymanagement (MM) back-off time value from the first type network;starting a PS MM back-off timer based on the received PS MM back-offtime value; and when the UE moves from a first cell of the first typenetwork to a second cell of the second type network, starting a locationarea update procedure, which is associated with the CS domain, while thePS MM back-off timer is running, wherein the first cell and the secondcell belong to a same location area, which is associated with the CSdomain.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an Evolved Packet System which isassociated with the Long Term Evolution (LTE) system.

FIG. 2 is a view illustrating an overall architecture of the E-UTRAN towhich the following technical features are applied.

FIG. 3 is a view illustrating EPS bearers crossing multiple interfaces.

FIG. 4 is a flowchart illustrating a procedure for ISR activation byusing TIN.

FIG. 5 is a block diagram showing reference architecture to whichCS-fallback function is applied.

FIG. 6 is a flowchart illustrating a situation where one of embodimentsis applied.

FIG. 7 is a flowchart illustrating a situation where one of embodimentsis applied.

FIG. 8 is a flowchart illustrating a procedure of applying cellreselection priority information included in an RRC Connection Releasemessage.

FIG. 9 is a flow chart illustrating a procedure handing the CS emergencycall-back and cell reselection priority information.

FIG. 10 is a flow chart illustrating a procedure of disabling the LTEcapability when the UE is unable to perform CS fallback.

FIG. 11 is a block diagram showing a wireless apparatus to implementtechnical features of this description.

DETAILED DESCRIPTION OF THE INVENTION

The technology described below can be used in various wirelesscommunication systems such as code division multiple access (CDMA), afrequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), etc. The CDMA canbe implemented with a radio technology such as universal terrestrialradio access (UTRA) or CDMA-2000. The OFDMA can be implemented with aradio technology such as institute of electrical and electronicsengineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20,evolved UTRA (E-UTRA), etc. The UTRA is a part of a universal mobiletelecommunication system (UMTS). The 3^(rd) generation partnershipproject (3GPP) long term evolution (LTE) is a part of an evolved UMTS(E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA in the downlinkand uses the SC-FDMA in the uplink. For clarity of explanation, thefollowing description will focus on the 3GPP LTE (or the 3GPP LTE-A).However, the technical features of this description are not limitedthereto.

FIG. 1 is a view illustrating an Evolved Packet System which isassociated with the Long Term Evolution (LTE) system. The LTE systemaims to provide seamless Internet Protocol (IP) connectivity between auser equipment (UE) and a pack data network (PDN), without anydisruption to the end user's application during mobility. While the LIEsystem encompasses the evolution of the radio access through an EvolvedUniversal Terrestrial Radio Access Network (E-UTRAN) which defines aradio protocol architecture between a user equipment and a base station,it is accompanied by an evolution of the non-radio aspects under theterm ‘System Architecture Evolution’ (SAE) which includes an EvolvedPacket Core (EPC) network. The LTE and SAE comprise the Evolved PacketSystem (EPS).

The EPS uses the concept of ‘EPS bearers’ to route IP traffic from agateway in the PDN to the UE. A bearer is an IP packet flow with aspecific Quality of Service (QoS) between the gateway and the UE. TheE-UTRAN and EPC together set up and release the bearers as required byapplications.

The EPC, which is also referred to as the core network (CN), controlsthe UE and manages establishment of the bearers. As depicted in FIG. 1,the node (logical or physical) of the EPC in the SAE includes a MobilityManagement Entity (MME) 10, a PDN gateway (PDN-GW or P-GW) 30, a ServingGateway (S-GW) 20, a Policy and Charging Rules Function (PCRF) 40, aHome subscriber Server (HSS) 50, etc.

The MME 10 is the control node which processes the signaling between theUE and the CN. The protocols running between the UE and the CN are knownas the Non-Access Stratum (NAS) protocols. Examples of functionssupported by the MME 10 includes functions related to bearer management,which includes the establishment, maintenance and release of the bearersand is handled by the session management layer in the NAS protocol, andfunctions related to connection management, which includes theestablishment of the connection and security between the network and UE,and is handled by the connection or mobility management layer in the NASprotocol layer.

The S-GW 20 serves as the local mobility anchor for the data bearerswhen the UE moves between eNodeBs. All user IP packets are transferredthrough the S-GW 20. The S-GW 20 also retains information about thebearers when the UE is in an idle state (known as ECM-IDLE) andtemporarily buffers downlink data while the MME initiates paging of theUE to re-establish the bearers. Further, it also serves as the mobilityanchor for inter-working with other 3GPP technologies including 2G and3G network, i.e., GPRS (General Packet Radio Service) and UMTS(Universal Mobile Telecommunications System).

The P-GW 30 serves to perform IP address allocation for the UE, as wellas QoS enforcement and flow-based charging according to rules from thePCRF 40. The P-GW 30 performs QoS enforcement for Guaranteed Bit Rate(GBR) bearers. It also serves as the mobility anchor for inter-workingwith non-3GPP technologies such as CDMA2000 and WiMAX networks.

The PCRF 40 serves to perform policy control decision-making, as well asfor controlling the flow-based charging functionalities.

The HSS 50, which is also referred to as a Home Location Register (HLR),contains users' SAE subscription data such as the EPS-subscribed QoSprofile and any access restrictions for roaming. Further, it also holdsinformation about the PDNs to which the user can connect. This can be inthe form of an Access Point Name (APN), which is a label according toDNS (Domain Name system) naming conventions describing the access pointto the PDN, or a PDN Address which indicates subscribed IP addresses.

Between the EPS network elements shown in FIG. 1, various interfacessuch as an S1-U, S1-MME, S5/S8, S11, S6 a, Gx, Rx and SGi are defined.

FIG. 2 is a view illustrating an overall architecture of the E-UTRAN towhich the following technical features are applied.

The E-UTRAN includes at least one eNB (evolved-Node B) 200 providing auser plane and a control plane towards a user equipment (UE) 210. The UEcan be fixed or mobile and can be referred to as another terminology,such as a MS (Mobile Station), a UT (User Terminal), an SS (SubscriberStation), an MT (mobile terminal), a wireless device, or the like. TheeNB 200 may be a fixed station that communicates with the UE 100 and canbe referred to as another terminology, such as a base station (BS), a NB(NodeB), a BTS (Base Transceiver System), an access point, or the like.

The protocols running between the eNBs 200 and the UE 210 are known asthe Access Stratum (AS) protocols.

The BSs (or eNBs) 200 are interconnected with each other by means of anX2 interface. The BSs 200 are also connected by means of the S1interface to the aforementioned Evolved Packet Core EPC elements, morespecifically to the Mobility Management Entity (MME) by means of theS1-MME and to the Serving Gateway (S-GW) by means of the S1-U.

The E-TURAN architecture depicted in FIG. 2 may further comprise a Homeevolved Node B (HeNB) 220 and an HeNB GW (HeNB gateway) 230.

The HeNB 220 is fundamentally similar to a typical eNB, but it can besimple devices typically installed by end users themselves. The HeNB 220is also referred to as an HNB (home NB), a femto cell, a home cellularbase station, etc. The HeNB 220 behaves like a cellular network withrespect to communication devices, which can use their regular cellularnetwork radio interface to communicate with them, and connects to acellular network operator's core network through the alternate networkaccess, such as Internet access via fiber, DSL or cable subscriptions.In general, the HeNB 220 has a low radio transmission output powercompared to the BS owned by mobile communication service providers.Therefore, the service coverage provided by the HeNB 220 is typicallysmaller than the service coverage provided by the eNB 200. Due to suchcharacteristics, the cell provided by the HeNB 220 is classified as afemto cell in contrast to a macro cell provided by the eNB 200 from astandpoint of the service coverage.

Hereinafter, the concept of an EPS bearer is explained. The EPS (EvolvedPacket System) uses the concept of EPS bearers to route IP traffic froma gateway in the PDN (pack data network) to the UE. The EPS bearer is anIP packet flow with a Quality of Service (QoS) between the gateway andthe UE. The E-UTRAN and EPC (Evolved Packet Core) together set up andrelease EPS bearers as required by applications.

The EPS bearer is typically associated with the QoS. Multiple bearerscan be established for a user in order to provide different QoS streamsor connectivity to different PDNs. For example, a user might be engagedin a voice (e.g., VoIP) call while at the same time performing webbrowsing or File Transfer Protocol (FTP) download. A VoIP bearer wouldprovide the necessary QoS for the voice call, while a best-effort bearerwould be suitable for the web browsing or FTP session.

Broadly, EPS bearers can be classified into two categories based on thenature of the QoS they provide. The two categories are MinimumGuaranteed Bit Rate (GBR) bearers and Non-GBR bearers. The GBR bearershave an associated GBR value for which dedicated transmission resourcesare permanently allocated at bearer establishment/modification. Bitrates higher than the GBR may be allowed for a GBR bearer if resourcesare available. On the other hand, the non-GBR bearers do not guaranteeany particular bit rate. For these bearers, no bandwidth resources areallocated permanently to the bearer.

Further, EPS bearers can be classified in a different manner. Inparticular, the EPS bearers can be classified into a default bearer anda dedicated bearer. The default bearer is an EPS bearer which is firstestablished for a new PDN connection and remains established throughoutthe lifetime of the PDN connection. The default bearer gets establishedwith every new PDN connection. Namely, when the UE connects to the P-GWby means of a procedure called ‘Initial Attach’, a new or default beareris created and its context remains established throughout the lifetimeof that PDN connection. The UE can be attached to more than one P-GW,and thus the UE can have more than one default bearer. The default EPSbearer is a non-GBR bearer and associated with a best effort QoS,wherein the best effort QoS is the lowest of all QoS traffic classes.Bearers which are not created at the initial attach procedure can bereferred to as dedicated bearers. The dedicated bearer is an EPS bearerthat is associated with uplink packet filters in the UE and downlinkpacket filters in the PDN GW where the filters only match certainpackets.

Hereinafter, the relationship of the EPS bearer and lower layer bearerssuch as S1, S5/S8, radio bearers and E-RAB is explained.

The EPS bearer has to cross multiple interfaces as shown in FIG. 3—theS5/S8 interface from the P-GW to the S-GW, the S1 interface from theS-GW to the eNodeB, and the radio interface (also known as the LTE-Uuinterface) from the eNodeB to the UE. Across each interface, the EPSbearer is mapped onto a lower layer bearer, each with its own beareridentity. Each node keeps track of the binding between the bearer IDsacross its different interfaces.

An S5/S8 bearer transports the packets of the EPS bearer between theP-GW and the S-GW. The S-GW stores a one-to-one mapping between an S1bearer and an S5/S8 bearer. Each bearer is identified by the GTP (GPRSTunneling Protocol) based Tunnel Endpoint ID (also known as a TEID)across both interfaces.

An S1 bearer transports the packets of an EPS bearer between the S-GWand the eNodeB. A radio bearer (also known as a radio data bearer)transports the packets of an EPS bearer between the UE and the eNodeB.Each bearer is identified by the GTP (GPRS Tunneling Protocol) tunnelendpoint ID (also known as a TEID or a GTP TEID) across both interfaces.

Further, the concept of the E-RAB (E-UTRAN Radio Access Bearer) may beused. An E-RAB transports the packets of an EPS bearer between the UEand the EPC (GPRS Tunneling Protocol), more specifically to the S-GWthrough eNB. When an E-RAB exists, there is a one-to-one mapping betweenthis E-RAB and an EPS bearer.

IP packets mapped to the same EPS bearer receive the same bearer-levelpacket forwarding treatment (e.g., scheduling policy, queue managementpolicy, rate shaping policy, or RLC configuration). Providing differentbearer-level QoS thus requires that a separate EPS bearer is establishedfor each QoS flow, and user IP packets must be filtered into thedifferent EPS bearers.

Hereinafter, the concept of Non-Access Stratum (NAS) states and AccessStratum (AS) states. A UE's behavior can be defined using a number ofstates, i.e., NAS and AS states, which describe whether the UE isregistered with the Evolved Packet Core (EPC) and whether it is activeor idle.

The first NAS states, i.e., EMM-REGISTERED and EMM-DEREGISTERED, areassociated with EPC mobility management (EMM) which is managed by theEMM protocol in the UE and the MME. The UE's EMM states depend onwhether the UE is registered with the EPC. In the state EMM-REGISTERED,the UE is registered with a serving MME and a serving gateway (S-GW) andhas an IP address and a default EPS bearer. In the stateEMM-DEREGISTERED, the UE is switched off or our of coverage.

The second NAS states, i.e., ECM-IDLE and ECM-CONNECTED, are associatedwith EPS connection management (ECM). These states are managed by theEMM protocol. The state ECM-IDLE is also referred to as EMM-IDLE, andthe state ECM-CONNECTED is also referred to as EMM-CONNECTED in acertain standard document (e.g., 3GPP TS 24.301) while terminologies‘ECM′-CONNECTED’ and ‘ECM-IDLE’ are preferred in other standarddocuments (e.g., 3GPP TS 23.401). The UE's ECM states depend of whetherthe UE is active or on standby, from a NAS protocol perspective. Anactive UE is in ECM-CONNECTED state. In this state, all the data bearersand signalling radio bearers are in place. When on standby, a mobile isin ECM-IDLE. In this state, it would be inappropriate to hold all thebearers in place. Therefore, the network tears down a UE's S1 bearer andradio bearers whenever the UE enters ECM-IDLE. However, the EPS bearersremain in place, and the S5/S8 bearers also remain in place. When inidle, the MME does not know exactly where an idle UE is located.Instead, the MME just knows which tracking area (TA) the UE is in. Thedetailed features of the TA will be described below.

The AS states are associated with a radio resource control (RRC). Thesestates are managed by the RRC protocol in the UE and a serving eNB. TheUE's RRC state depends on whether it is active or idle, from an ASprotocol perspective. An active UE is in RRC_CONNECTED state. In thisstate, the UE is assigned to a serving eNB, and can freely communicateusing signalling message on Signalling Radio Bearers 1 (SRB1). When onstandby, a UE is in RRC_IDLE. Mobility control in RRC_IDLE isUE-controlled (cell-reselection), while in RRC_CONNECTED it iscontrolled by the E-UTRAN (handover).

Hereinafter, the concept of mobility management (MM) and a tracking area(TA) (MM) is explained in detail. All UE-related information in theaccess network can be released during periods of data inactivity, i.e.,the ECM-IDLE. The MME retains the UE context and information about theestablished bearers during the idle periods.

To allow the network to contact a UE in the ECM-IDLE, the UE updates thenetwork as to its new location whenever it moves out of its currentTracking Area (TA). This procedure is called a ‘Tracking Area Update(TAU)’, and a similar procedure is also defined in a universalterrestrial radio access network (UTRAN) or GSM EDGE Radio AccessNetwork (GERAN) system and is called a ‘Routing Area Update (RAU)’. TheMME serves to keep track of the user location while the UE is in theECM-IDLE state.

When there is a need to deliver downlink data to the UE in the ECM-IDLEstate, the MME transmits a paging message to all base stations (i.e.,eNodeBs) in UE registered tracking area(s) (TA). Thereafter, eNBs startto page the UE over the radio interface. On receipt of a paging message,the UE performs a certain procedure which results in changing the UE toECM-CONNECTED state. This procedure is called a ‘Service RequestProcedure’. UE-related information is thereby created in the E-UTRAN,and the bearers are re-established. The MME is responsible for there-establishment of the radio bearers and updating the UE context in theeNodeB.

When the above-explained mobility management (MM) is applied, a mobilitymanagement (MM) back-off timer can be further used. Upon receipt of atime value associated with the MM back-off timer, the UE may activatethe MM back-off timer according to the time value given by the network.Under the current 3GPP specification, while the MM back-off timerassociated with PS domain is running, UE is prohibited from performingthe Tracking Area Update or Routing Area Update to the network. However,even when the MM back-off timer is running, the UE can receive a pagingmessage and be thereby paged, if the network has downlink data for theUE. As explained above, when the UE responding the page message, theService Request Procedure is required under the current 3GPPspecification.

Hereinafter, the concept of an idle mode signalling reduction (ISR)function is explained in detail. The ISR function serves to enhancebattery efficiency of the UE by reducing signaling for locationregistration (i.e., location update/registration update) when the UEmoves between different access networks such as E-UTRAN and UTRAN/GERAN.When the UE camps on the E-UTRAN cell, the UE performs locationregistration on the MME. ‘Camping on’ indicates that a UE has completeda cell selection/reselection process and has chosen a cell. In themeantime, when the UE moves to the UTRAN/GERAN cell and camps on thatcell, the UE performs location registration on the SGSN. Therefore, whenthe UE frequently moves between the E-UTRAN and the UTRAN/GERAN, the UEbattery life may be shortened due to frequent location registrationprocedures. In order to reduce the battery impact when UE moving betweentwo different RATs (Radio Access Technology)s, the ISR function has beenused to avoid the repeated registration.

According to the ISR function, once the UE respectively performslocation registration on the MME and the SGSN (two mobility managementnodes) via the E-UTRAN and the UTRAN/GERAN, the UE in an idle mode doesnot perform an additional location registration when moving between twopre-registered Radio Access Technologies (RATs), or when reselecting acell in one of the registered areas. If there is downlink (DL) data thatshould be sent to a corresponding UE in an ISR activated state and anidle mode, paging is simultaneously delivered to the E-UTRAN and theUTRAN/GERAN. This allows the network to successfully search for the UEand to deliver the DL data to the UE.

Hereinafter the concept of ‘TIN’ is explained in detail. When a UEaccesses a network, the network may allocate a temporary identity to theUE. For instance, a 2G/3G network (e.g., GERAN/UTRAN) allocates a PacketTemporary Mobile Subscriber Identity P-TMSI to the UE, while the SAEsystem allocates a Global Unique Temporary Identity (GUTI) to the UE.Since the UE may move between different networks (e.g.,GERAN/UTRAN/E-UTRAN), when the UE in idle mode reselects a cellcontrolled by a new CN node, the original CN node, which maintains theUE context, needs to be found by using a temporary identity of the UE,which was assigned by the original CN node and can be used to identifythe original CN node and the UE context, to obtain the context of theUE. Therefore, when using the ISR function, the UE hold a TemporaryIdentity used in Next update (TIN), which is a parameter indicatingwhich type of temporary identity shall be used in the next signalingwith the core network, which can be TAU or RAU. Possible values of TINinclude ‘GUTI’ (i.e., the UE's identification known to the MME),‘P-TMSI’ (i.e., the UE's identification known to the SGSN) and ‘RATrelated TMSI’. For instance, in a situation where the TIN is set to theGUTI, the new SGSN can fetch the UE's context from the old MME byreceiving a RAU request with an identity mapped from the GUTI. While theGUTI is not a native identification to the SGSN, context exchange can beperformed by using the identity mapped from the GUTI.

FIG. 4 is a flowchart illustrating a procedure for ISR activation byusing the TIN. In step S410, in a case where no ISR is activated, anormal attach is performed in the E-UTRAN. As a result, the UE sets itsTIN to ‘GUTI’. As discussed above, once the TIN is set to ‘GUTI’, the UEuses ‘GUTI’ for a subsequent TAU or RAU procedure.

In step S420, the UE now selects GERAN/UTRAN as its desired accessalthough it stays in the idle mode. The UE transmits a RAU request tothe SGSN by using the ‘GUTI’ as indicated by its TIN. In particular, theUE transmits a RAU request to the SGSN including a P-TMSI and a RotingArea Identity (RAI), which are mapped from the GUTI.

In step S430, the SGSN fetches from the MME the UE's context, and theMIME indicates ISR support. In step S440, registration of SGSN with theHSS is performed.

In step S450, an indication for ISR activation is included in the RAUaccept message. Under the current 3GPP specification, the UE sets itsTIN to ‘RAT related TMSI’ when the ISR function is activated. When theTIN is set to ‘RAT related TMSI’, a UE's identification for a subsequentTAU or RAU procedure is determined by the type of RAT which the UE iscurrently camping on. Namely, when the TIN is set to ‘RAT related TMSI’,the UE uses the GUTI when camping on an E-UTRAN cell and uses the P-TMSIwhen camping on a GERAN/UTRAN cell.

Hereinafter, the concept of CS-fallback function is explained. Asdiscussed above, 3GPP technology specifies fallback for circuit switchedservices associated with the CS domain. The CS-fallback in the EPSenables the provisioning of voice and traditional CS-domain services,and LTE may reuse CS infrastructure when the UE is served by LTE. ACS-fallback enabled UE, connected to E-UTRAN may use GERAN or UTRAN toconnect to the CS domain. This function is available in case E-UTRANcoverage is overlapped by either GERAN coverage or UTRAN coverage.

FIG. 5 is a block diagram showing reference architecture to which theCS-fallback function is applied. Referring to FIG. 5, the referencearchitecture includes a visitor location register (VLR) 510, the MME520, the SGSN 530, the RNC 540, the eNB 550. Between the networkelements shown in FIG. 5, various interfaces such as an A/Iu-cs, SGs,and Gb/Iu-ps are defined.

The VLR 510 contains CS subscriber data required for CS call handlingand mobility management context for mobile subscribers currently locatedin the area controlled by the VLR. In particular, the VLR 510 maintainsthe UE's CS context. The VLR 510 can be included in a mobile switchingcenter (MSC) and referred to as a MSC/VLR.

The CS fallback capable UE in E-UTRAN coverage which has been registeredto the MME 520 and the VLR 510 can be paged for the CS or the PSservices using a CS or a PS paging message, respectively. The CS pagingcan be initiated by the VLR 510 and the PS paging can be initiated bythe MME 520. The CS paging can be transmitted from the VLR 510 to MME530, although the MME 530 is an entity handling the UE's PS context.When the CS paging is given to the eNB 550, the eNB 550 pages the UE byincluding an indicator indicating the CS paging is transmitted. Inresponse to the CS paging, the UE initiates an extended service requestprocedure to the MME 520. The MME 520 then decides whether to allow theUE's operation in CS domain, thereby enabling the eNB 550 to performsubsequent procedures such as PS handover or redirection to the CSdomain. Finally, the UE finishes CS services such as a CS voice call andthereafter moves back to E-UTRAN.

As discussed above, the CS fallback capable UE which has been registeredto the MME 520 and the VLR 510 may enter the GERAN/UTRAN coverage fromE-UTRAN coverage due to the CS paging. However, the UE may enter theGERAN/UTRAN coverage even when no CS paging is received, i.e. when UEmoving out of E-UTRAN coverage. In this situation, the UE performs theRAU procedure to the PS domain if the ISR function is notenabled/activated. Furthermore, UE may need to perform a location areaupdate procedure to update the UE's location with VLR in a situationthat GERAN/UTRAN cell's Location Area Identity is not the same as whatUE previously registered to when in E-UTRAN. The RAU procedure isassociated with the PS domain for location update purposes, while a‘location area update (LAU)’ procedure is the one for the CS domain. Ingeneral, the coverage of the location area (LA) for the CS domain isgreater than that of the routing area (RA) or Tracking Area (TA).

In order to perform the LAU, LA code should be received by a broadcastchannel. The LA code is combined with a PLMN-ID, which is already knownto the UE, and thus the UE may detect the LA code by checking thebroadcast channel. The identification (ID) information containing thePLMN-ID and the LA code can be referred to as LA identification (LAI).

The CS fallback capable UE may already have an old LAI before it entersthe GERAN/UTRAN coverage, since the old LAI may be given when previouslyregistered to the VLR 510. Under the current 3GPP standards, if the UEreceives a different LAI different from the old one, it performs the LAUto the new network. Otherwise, the UE does not perform the LAU. It islikely that UE is still within the same LA when moving out of E-UTRAN toGERAN/UTRAN cells. In this situation, if TIN indicates GUTI, the UE onlyperforms RAU to SGSN 530 and does not performs LAU to the VLR 510. TheRAU procedure may or may not enable ISR for the UE. Because VLR 510 isnot informed that UE has moved to GERAN/UTRAN, when CS calls arrives,the VLR 510 will still request MME 520 to perform paging. If the ISR isnot enabled, the MME will inform the VLR 510 that UE has moves out ofMME controlled area, such that VLR 510 should perform CS paging inGERAN/UTRAN cells in the same LA. If the ISR is enabled, the MME 520will performs the CS paging in E-UTRAN, and it also informs the SGSN 530to perform CS paging concurrently in UTRAN/GERAN.

The aforementioned MM backoff timer can be signaled for two core networkdomains, i.e., a PS and CS MM backoff timers. Further, a UE is preventedfrom performing the LAU while the CS MM backoff timer is running and aUE is prevented from performing RAU/TAU while the PS MM backoff timer isrunning.

In the communication system depicted in FIG. 5 may have a technicalproblem in which the UE becomes unreachable when the CS paging isinitiated. The problem may occur when the CS fallback capable UE hasfinished a combined registration (UE's registration in both PS and CSdomains) but has not received the CS paging yet. For the UE the ISRfunction is not activated, and the UE may have received a PS MM backofftime value and started the PS MM backoff timers before performing theRAU procedure when moving to GERAN/UTRAN. In a case where the UE in theabove situations camps on an LTE cell and eventually receives a CSpaging, there would be no technical problem since the MME to which theUE was registered handles the CS paging. However, in a case where the UEin the above situations camps on a GERAN/UTRAN cell during PS MM backofftimer is running and eventually VLR receives a incoming call to the UE,the above technical problem occurs, since the UE has not finished a RAUprocedure due to the PS MM backoff timer and the VLR, MME has no updatedinformation on the UE's registration.

It is noted that the above problem cannot be solved by merelymanipulating the PS MM backoff timer. In particular, if the LA of theGERAN/UTRAN cell is different from what UE has registered in E-UTRAN,the UE may receive the CS paging, if the LAU is successfully performedand the CS paging is successfully delivered to the RNC. However, in acase where the UE has the same LAI as the previous one and the RAU isnot successfully performed due to PS MM backoff, the above technicalproblem still occurs since the UE's LAU attempt is prevented and the RAUis the only procedure to update the UE's location.

The first embodiment of the present description solve the abovetechnical problem. In particular, the first embodiment proposes toperform the LAU in a certain situation. The first embodiment isapplicable to a case where the ISR is disabled, the old and new LAIs areidentical, and PS MM backoff timer (i.e., T3346) is running. In thiscase, the first embodiment proposes to perform the LAU operation,thereby delivering the updated UE information to the VLR via the LAUoperation.

In other words, the first embodiment is applicable to a case where: i)the UE successfully performed a combined TAU in LTE, with ISR disabled;ii) the UE later performs another TAU or RRC connection request butrejected with T3346; iii) the UE moves out of LTE coverage and enters anarea with 2G/3G only in the same LA; and iv) the UE cannot performRouting Area Updating (RAU) due to T3346 running; The first embodimentincludes features in which when UE reselects from S1 mode (LTE) to A/Gbor Iu (2G/3G) mode while T3346 is running, and if UE will be monitoringCS page in 2G/3G, the UE should do the location area update (LAU) eventhe LA has not changed after the reselection.

The first embodiment is applicable to a case where the ISR is notenabled. However, the present description further provides the secondembodiment applicable to a case where the ISR is enabled.

FIG. 6 is illustrating a situation where the second embodiment isapplied. If the UE moves between the tracking area (TA) 610 and routingarea (RA) 620 for which the ISR function is enabled, the above technicalproblem may not occur. In particular, if the ISR function is enabledwith respect to TA 610 and RA 620, the MME and SGSN which are associatedwith TA 610 and RA 620 maintain the UE context. Therefore, even if theCS paging is initiated in the VLR, it will be delivered to the SGSN viathe MME from the VLR, and therefore the UE will receive the paging viathe RNC.

However, if the UE enters from TA 610 to RA 630 while the ISR functionis enabled between TA610 and RA1 620, the aforementioned CS paging issuemay still occur because the MME would still request paging in RA1 620instead of RA2 630. Therefore, the second embodiment does not requirethe ISR function to be disabled when performing the LAU operation if theold and new LAI are identical, and if the PS MM backoff timer isrunning.

FIG. 7 is a flowchart showing an example of a method combining a numberof embodiments. The method of FIG. 7 is applicable to system comprisingan E-UTRAN side having the MME handling the PS domain and the VLRhandling the CS domain.

Referring to FIG. 7, in step S710, the CS fallback capable UE performs acombined track area update (TAU) to E-UTRAN, thereby registering theUE's updated information to the MME and the VLR. In other words, theUE's location is updated in PS and CS domains.

In step S720, the UE receives a PS mobility management (MM) back-offtime value from the E-UTRAN. The PS MM back-off timer value can beincluded in various messages such as an RRC connection release message,an RRC connection reject message, a RAU reject message, and/or a TAUreject message.

In step S730, upon receiving the PS MM back-off time value, the UEinitiates the PS MM back-off timer. As discussed above, while the PS MMback-off timer is running, a subsequent RAU is prohibited.

In step S740, when entering from a E-UTRAN cell to a GERAN/UTRAN cellboth belonging to same location area (LA), the UE starts the LAU, whilethe PS MM back-off timer is running.

Accordingly, the example of FIG. 7 is applicable to a case in which: i)the UE successfully performed a combined TAU in LTE, with ISR disabledor enabled; ii) the UE later performs another TAU or RRC connectionrequest but rejected with T3346; iii) the UE moves out of LTE coverageand enters an area with 2G/3G only in the same LA; iv) the UE cannotperform Routing Area Updating (RAU) due to T3346 running; The first andsecond embodiments include features in which when the UE reselects fromS1 mode (LTE) to A/Gb or Iu (2G/3G) mode while T3346 is running, and ifthe UE will be monitoring CS page in 2G/3G, the UE should do thelocation area update (LAU). Further, a condition triggering the LAU canbe further narrowed to apply to UEs with ISR deactivated with its TINset to the ‘GUTI’. In addition, a condition triggering the LAU can befurther narrowed to apply to UEs with ISR activated with its TIN set to‘RAT related TMSI’ but moves to a different RA than previouslyregistered.

Further, the above triggering condition of the LAU can be furthermodified. In particular, the example of FIG. 7 is a case where the UEcannot perform MM procedure in the PS domain since the T3346 iscurrently running. However, the above technical features are applicableto a case where the mobile originated (MO) signaling for the PS domainis prohibited by access barring or enhanced access barring. In 3GPP,various access barring can be applied to the UE. In particular, randomaccess procedure can be prohibited by an Access Class (AC) barring. Fora certain type of UEs, if a UE initiates an MO call or MO signaling, theUE draws a random number. If the drawn number is lower than theprobability factor, access is not barred. Otherwise access is barred fora duration which is randomly selected based on the broadcasted barringtimer value. The enhanced access barring further extends thefunctionality and may be associated with roaming. In particular, whennetwork congestion occurs, the operator may block the access of visitingusers by barring the roaming UEs' access.

When the mobile originated (MO) signaling for the PS doming isprohibited by access barring or enhanced access barring, the aboveproblem also occurs. Therefore, the above features are also applicableto a case where the UE cannot perform MM procedure in the PS domain dueto the access barring or enhanced access barring.

Hereinafter, the third embodiment related to a CS emergency call and CSpaging. The UE may make an emergency call connection with a PublicSafety Answering Point (PSAP). The PSAP, sometimes called Public SafetyAccess Point, is a call center responsible for answering calls to anemergency telephone number for emergency services such as police,firefighting, and ambulance services. The emergency call can beestablished in the CS or PS domain.

In general, the UE in the PS domain may initiate a PS emergency call,but there is a situation where the UE in the PS domain attempts a CSemergency call. For instance, if the E-UTRAN network does not supportemergency bearer services in S1 mode, the UE may attempt to access theGERAN/UTRAN to set up the emergency call by using the CS domain.

When a PS/CS call is completed, an RRC connection for the UE may bereleased with a timer T320 in E-UTRAN, T322 in UTRAN or T3230 in GERAN.In E-UTRAN, the RRC Connection Release message includes a‘idleModeMobilityControlInfo’ field, which indicates cell reselectionpriority information. Similarly the dedicated reselection priorities canbe signaled in UTRAN/GERAN. The cell reselection priority informationindicates priority of radio access network for a subsequent access. TheT320, T322, T3230 is used for the cell reselection priority information.In particular, information of the ‘idleModeMobilityControlInfo’ isregarded to be valid while the T320 is running. Once the timer expires,the UE may detect a broadcast channel and determine what type of radioaccess network (e.g., LTE/3G/2G) is the best priority for a subsequentaccess.

FIG. 8 show a procedure of applying the cell reselection priorityinformation included in the RRC Connection Release message. Referring toFIG. 8, in step S810, the UE's RRC Connection for the emergency call isreleased and the ‘idleModeMobilityControlInfo’ field is received. Sincethe timer 320 is included in the RRC Connection Release message from theE-UTRAN, cell reselection priority information of the‘idleModeMobilityControlInfo’ will be applied while the T320 is running.In step S820, the UE may initiate the emergency call to the GERAN/UTRAN.After establishing the emergency call, in step S830, the RRC connectionfor the emergency call is released, but the dedicated reselectionpriorities is not included in the new RRC Connection Release message. Inthis case, a time duration 840 is a period to which the previous‘idleModeMobilityControlInfo’ field received from the LTE is applied.After the T320 expires, the UE applies cell reselection priorityinformation which is broadcast in the system information.

The emergency call to the PSAP may be dropped for various reasons. Inthis situation, the PSAP will attempt an emergency call-back to theoriginal UE. For instance, a CS emergency call from a UE which hasperformed the combined TAU to the MME and the VLR may be dropped. If theUE has not performed RAU to the GERAN/UTRAN, stays in the same LA, andreselects back to E-UTRAN after the CS emergency call, the UE's previousinformation in the VLR is correct, and a CS paging for emergencycall-back to the UE can be properly handled by the VLR. Therefore, anemergency call-back to the original UE from the PSAP will be properlyhandled by the VLR.

However, there may occur a technical problem when handing the CS pagingas depicted in FIG. 9. FIG. 9 is a flow chart illustrating a procedurehanding the CS emergency call-back and cell reselection priorityinformation. The specific order of steps in FIG. 9 is shown forexemplary purposes, and the present description is not limited thereto.Referring to FIG. 9, in step S910, the MM-BO timer (i.e., T3346) isrunning between the UE and the MME for various reasons (e.g., RRCConnection Reject due to network congestion). Thereafter, as depicted insteps S920-930, the UE may perform the LAU procedure and initiate a CSemergency call. However, as depicted in steps S940, the emergency callmay be dropped and the UE may still have a valid reselection prioritywith E-UTRAN being the highest priority RAT.

If the dedicated reselection priority (which may come from a prior RRCconnection release in E-UTRAN before the CS emergency call with timerT320), which designate an E-UTRAN cell as the highest priority cell,there occurs a technical problem in which the CS-paging for theemergency call-back cannot be delivered to the UE. This is because, theUE has performed LAU is 2/3G area but cannot perform combined TAU whenreselecting back to the E-UTRAN cell before the T3346 expires.Therefore, the VLR, which only holds incorrect information that the UEhas entered the GERAN/UTRAN by the LAU operation (S920), cannot properlyhandle the CS-paging for the emergency call-back.

Therefore, the third embodiment of the present description proposes todisable the LTE capability (i.e., E-UTRA capability) in the abovesituation. In other words, the third embodiment is applicable to a casewhere the UE is unable to perform a combined TAU after emergency CSfallback. Examples of a case includes various situations such as a casein which: i) the UE successfully performed a combined TAU in the LTE;ii) the UE later performs another TAU or RRC connection request butrejected with the timer T3346, and the ‘IdleModeMobilityControlInfo’indicates the LTE with the highest priority and includes the timer T320;iii) the UE makes an emergency call and performs the LAU before/afterthe call; and iv) the UE selects back to a LTE cell of the same ordifferent TA after the emergency call finishes while the T320 and T3346are still running.

The above problematic case can be resolved by mandating the UE stays inthe GERAN/UTRAN after the CS emergency call, instead of reselecting backto the E-UTRAN. Namely, the LTE capability can be disabled, such thatRRC reselection priority can be ignored by the UE.

FIG. 10 is a flow chart illustrating a procedure of disabling the LTEcapability when the UE is unable to perform combined TAU after aemergency CS fallback. Referring to step S1010, the UE performing acombined TAU to the MME and VLR. In step S1020, the UE receiveinformation indicating LTE as the higher priority compared to 2/3G RATs.The information indicating LTE reselection priority can be included inthe ‘idleModeMobilityControlInfo’ field of the RRC release message.Further, the information can be delivered to the UE with the timer T320.In steps S1030-S1040, the UE determines whether it is unable to receivea CS paging from the LTE, and when the UE is determined to be unable toreceive the CS paging from the LTE, then the UE disables the LTEcapability before or after establishing the CS emergency call.

FIG. 11 is a block diagram showing a wireless apparatus to implementtechnical features of this description. This may be a part of a UE, orcore network (CN) entity. The wireless apparatus 1000 may include aprocessor 1010, a memory 1020 and a radio frequency (RF) unit 1030.

The processor 1010 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 1010. Theprocessor 1010 may perform procedure and embodiments described above.The memory 1020 is operatively coupled with the processor 1010, and theRF unit 1030 is operatively coupled with the processor 1010.

The processor 1010 may include application-specific integrated circuit(ASIC), other chipset, logic circuit and/or data processing device. Thememory 1020 may include read-only memory (ROM), random access memory(RAM), flash memory, memory card, storage medium and/or other storagedevice. The RF unit 1030 may include baseband circuitry to process radiofrequency signals. When the embodiments are implemented in software, thetechniques described herein can be implemented with modules (e.g.,procedures, functions, and so on) that perform the functions describedherein. The modules can be stored in the memory 1020 and executed by theprocessor 1010. The memory 1020 can be implemented within the processor1010 or external to the processor 1010 in which case those can becommunicatively coupled to the processor 1010 via various means as isknown in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope of the present disclosure.

What has been described above includes examples of the various aspects.It is, of course, not possible to describe every conceivable combinationof components or methodologies for purposes of describing the variousaspects, but one of ordinary skill in the art may recognize that manyfurther combinations and permutations are possible. Accordingly, thesubject specification is intended to embrace all such alternations,modifications and variations that fall within the scope of the appendedclaims.

What is claimed is:
 1. A method of updating control information relatedto a location of a user equipment (UE) supporting a first type networkand a second type network different from the first type network, themethod performed by the UE and comprising: when the UE enters a cell ofthe second type network from the first type network, determining tostart a location updating procedure which updates a location area of theUE if a mobility management (MM) back-off timer in the UE is running,the UE's Temporary Identity used in Next update (TIN) is set to a GlobalUnique Temporary Identity (GUTI), and a location area of a current cellis equal to a location area stored in the UE; and starting the locationupdate procedure, wherein the MM back-off timer is a timer running whenan MM back-off timer value is received by the UE.
 2. The method of claim1, wherein the first type network includes a mobility management entity(MME) handling a packet switched (PS) domain and a visitor locationregister (VLR) handling a circuit switched (CS) domain.
 3. The method ofclaim 1, wherein the first type network is an Evolved UniversalTerrestrial Radio Access Network (E-UTRAN).
 4. The method of claim 1,further comprising: performing a combined track area update (TAU) to thefirst type network.
 5. The method of claim 4, further comprising:receiving a TAU accept message indicating whether an idle mode signalingreduction (ISR) function is enabled.
 6. The method of claim 1, furthercomprising: performing an intersystem change from the first type networkto the second type network before starting the location area updateprocedure.
 7. The method of claim 1, wherein the UE is configured to usea CS fallback.
 8. The method of claim 1, wherein the MM back-off timervalue is received from a Mobility Management Entity (MME).
 9. A userequipment (UE) for updating control information related to a location ofa user equipment (UE) supporting a first type network and a second typenetwork different from the first type network, the UE comprising: aradio frequency unit configured to communicate a signal; and a processorcoupled to the radio frequency unit and configured to: when the UEenters a cell of the second type network from the first type network,determine to start a location updating procedure which updates alocation area of the UE if a mobility management (MM) back-off timer inthe UE is running, the UE's Temporary Identity used in Next update (TIN)is set to a Global Unique Temporary Identity (GUTI), and a location areaof a current cell is equal to a location area stored in the UE; andstart the location update procedure, wherein the MM back-off timer is atimer running when a MM back-off timer value is received by the UE. 10.The UE of claim 9, wherein the first type network includes a mobilitymanagement entity (MME) handling a packet switched (PS) domain and avisitor location register (VLR) handling a circuit switched (CS) domain.11. The UE of claim 9, wherein the first type network is an EvolvedUniversal Terrestrial Radio Access Network (E-UTRAN).
 12. The UE ofclaim 9, wherein the processor is further configured to perform acombined track area update (TAU) to the first type network.
 13. The UEof claim 12, wherein the processor is further configured to receive aTAU accept message indicating whether an idle mode signalling reduction(ISR) function is enabled.
 14. The UE of claim 9, wherein the processoris further configured to perform an intersystem change from the firsttype network to the second type network before starting the locationarea update procedure.
 15. The UE of claim 9, wherein the UE isconfigured to use a CS fallback.
 16. The UE of claim 9, wherein the MMback-off timer value is received from a Mobility Management Entity(MME).